Potencia in air conditioning is cooling power or thermal power, and it can be called that, but the usual word is capacity. References to the "thermal power" of air conditioning systems are unusual; thermal design power, in Iseut's reference, specifically applies to computer cooling systems.

To be picky, "inferior a" doesn't mean not exceeding, it means less than. 25 kW does not exceed 25 kW but it is not "inferior a 25 kW".

"kW térmicos" is used in Spanish, but in English we just say kW. This is one of several units in the English-speaking world used to measure the capacity of AC systems: BTUs (British thermal units), which are equal to the "frigorías" that people refer to in Spain, tons and HP.

"Thermal kW" are not the same as electrical kW, but the context shows which we're talking about.

This page explains the difference between "potencia térmica (capacidad)" and "potencia eléctrica (consumo)" with an illustration of a bilingual Italian/English AC specification plate, where "potenza resa" (thermal power) is called "capacity" and "potenza assorbita" (electrical power) is called "input":
http://nergiza.com/energia-termica-vs-energia-electrica/

"Kilowatt (kW)
Measure of energy flow used to express the cooling capacity, heating capacity and power consumption of an air conditioning system."
HVAC Glossary of terms
http://www.airedale.com/web/About-Airedale/HVAC-Air-Conditio...

"Divide the number of kilowatts by 2.55 to convert from kW to HP. For example, if your air conditioner's capacity was 10 kW, you would divide 10 by 2.55 to get about 3.92 HP."
http://classroom.synonym.com/convert-kw-hp-air-conditioners-...

"Cooling capacity is the measure of a cooling system's ability to remove heat. The SI units are watts (W). Other common units include tons, and tonnes, which describe the amount of water at a given temperature that can be frozen in a given amount of time."
https://en.wikipedia.org/wiki/Cooling_capacity

"How to convert an air conditioner capacity from Btu to kW. What is "ton"?
1 horsepower (HP) = 2.8 kW
1 kW*hr = 3,413 BTU/hr (British Thermal Units),
1 ton = 12,000 BTU/hr"
http://www.ahi-toshiba.com/buyer/faq.php

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Note added at 16 hrs (2016-11-29 13:04:14 GMT)
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I found it confusing too until I read up on it. Using the same unit in two different senses seems messy, but nobody in the business seems to mind or get confused. As long as you talk about capacity and input it's clear which sort of kW you mean, so you don't have to say you mean thermal not electrical kW, but "potencia" is ambiguous, so you have to specify in Spanish. This is a good reason for not translating it as "power", it seems to me. The two types of kW are significantly different in practice. A system with a cooling capacity of 25 (thermal) kW uses much less that 25 (electrical) kW of input — fortunately, or AC would be prohibitively expensive to run.